fix(ui): remove dead delete API method and add confirmation for delete-by-source

- Remove duplicate `delete` method (identical to `remove`)
- Route delete-by-source through confirmation dialog with source
  locator displayed and "Remove all from source" button

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/api/companySkills.ts

@@ -64,8 +64,4 @@ export const companySkillsApi = {
       `/companies/${encodeURIComponent(companyId)}/skills/${encodeURIComponent(skillId)}/install-update`,
       {},
     ),
-  delete: (companyId: string, skillId: string) =>
-    api.delete<CompanySkill>(
-      `/companies/${encodeURIComponent(companyId)}/skills/${encodeURIComponent(skillId)}`,
-    ),
 };